Rochester carbs have a bad habit of warping the top cover, which creates an internal vacuum leak that keeps the power valve open most of the time, creating an over rich mixture. There is a procedure to straighten the cover which works at least temporarily. Make that carb a stinky paperweight and find a Carter carb to be a long term solution. White smoke is usually condensation in the exhaust system, which will be resolved by a highway run under load. If the engine has been idle for a long period of time, the rings might be stuck in the grooves in the pistons, resulting in low compression and oil consumption. I add 2-3 quarts of Diesel fuel to a full crankcase of cheap oil, and run the engine at a fast idle for 20-30 minutes. DO NOT drive the vehicle or put the engine under any kind of load with the thinned out oil on board. The crankshaft and rods splashing into the overfilled sump will splash the inside of the engine like the agitator in a washing machine, dissolve sludge and debris, and free up the rings. Drain the hot oil and refill with 15W-40, and change the oil filter.
Jerry
